The present invention relates to a method and apparatus for performing intramuscular stimulation.
It has been determined by a number of workers that severe chronic musculoskeletal pain caused by muscles shortening within the body, can be relieved by a technique similar to acupuncture. However, unlike in acupuncture, this method known generally as xe2x80x9cintramuscular stimulationxe2x80x9d (IMS), involves the insertion of a needle into a region where the nerves connect with the muscle, the motor point region, where the muscle may be readily stimulated or xe2x80x9ctwitchedxe2x80x9d.
The stimulation of the muscle is effected by either mechanical manipulation, electrical stimulation or a combination of both.
In many cases the technique necessitates multiple needle insertions into the body of a patient and often at many sites in an affected region. Conventionally, IMS has been performed manually by a physician. This manual technique is very tiring for the physician and has even been known to cause repetitive strain injury. This is because conventional manual stimulation of the muscles is achieved by inserting the needle to the motor point where the muscle may be stimulated so as to cause the muscle to twitch.
Manual stimulation generally involves a reciprocal motion of the needle for a number of seconds. The muscle then relaxes after removal of the needle.
A second method of stimulation is to pass an electric current into the motor point region which causes similar stimulation of the muscle. This can be advantageous as the electric current may stimulate a number of muscles in the area surrounding the needle. Alternatively a combination of manual and electrical IMS has also been found to be effective.
An example of the automation of this method is disclosed in U.S. Pat. No. 5,968,063 and U.S. Pat. No. 6,058,938. In this case one end of a conventional acupuncture or electromyography (EMG) needle is attached to a coupling device which in turn is coupled to the drive mechanism of a gun. In use, the gun is placed against the skin and the second end of the needle is driven from the end of the gun through a nozzle touching the skin and into the patient.
Although the use of automatic devices represents a significant advance upon manual manipulation, there are a number of problems associated with them.
Conventional EMG and acupuncture needles are available in a number of different sizes according to the depth of penetration which should be used. Some problems are encountered in attaching these various different size needles to the coupling device of the gun whilst maintaining the integrity and sterility of the needles. In addition, if the subject requires treatment of different muscular groups within the body, the use of different needles having different lengths is therefore required, necessitating a change of needles between the treatments of different muscle groups.
In accordance with a first aspect of the present invention, we provide a disposable needle applicator unit for attachment to an intramuscular stimulation device, the applicator unit comprising:
a needle having an elongate first end portion for insertion into the body of a subject and a second end portion for coupling with a drive carriage of the intramuscular stimulation device; and
an elongate sheath for enclosing at least the first end portion of the needle, the sheath having a first opening in one end from which the first end portion of the needle may be extended, and a second opening allowing the second end portion of the needle to be coupled with the drive carriage.
The use of a disposable needle applicator unit provides many advantages, particularly in that the sterility of the needle may be more readily assured. The needle applicator unit may be conveniently coupled directly to the drive carriage of the intramuscular stimulation device whilst the sheath provides protection of the portion of the needle that is to be inserted into the body.
As the needle is contained safely within the sheath when the applicator unit is being fitted or attached to the device, the risk of cross-contamination between the patient and physician due to accidental penetration of the physician""s skin with the needle, is significantly reduced. The unit therefore provides a further advantage in that, following use, it can be detached from the IMS device and disposed of in its entirety.
Typically the first opening of the sheath will be arranged to tightly enclose the needle so as to precisely guide the first end portion of the needle into the subject in a rectilinear manner with a minimum amount of needle distortion, which is known to cause discomfort in the subject.
Although the second opening of the sheath may be arranged in a number of locations allowing access to the needle, preferably it will take the form of a slot arranged in the side of the sheath such that the second end portion of the needle may be coupled to the drive carriage of the IMS device.
The drive carriage may be arranged such that a coupling element passes through the opening of the sheath to couple with the needle. However, in general the second end portion of the needle will be arranged to project through the second opening of the sheath in order to couple externally to the drive carriage. This may be achieved for example by arranging the second end portion of the needle to be at an angle with respect to the first end portion, for example projecting through the second opening slot.
The first end portion of the needle may then move in the first direction through the first opening of the sheath, as the second end portion moves along the slot whilst projecting from it. In this way a single needle may be used for performing an IMS cycle at different penetration depths upon different muscle groups.
Typically at least the first end portion of the needle will be coated in a friction reducing layer such as PTFE. However, the coating may be removed at the extreme tip of the first end portion where the needle may be sharpened. This allows the tip of the needle to make a good electrical contact with the motor point of the subject.
The needle may be formed as a single component. Preferably however the needle will comprise two or more components. Typically therefore the needle may comprise first and second elongate components arranged axially end to end and coupled such that the first end portion is formed from part of the first component and the second end portion is formed from the second component. The second elongate component may be arranged with an internal bore within which part of the first elongate component may be received.
The two components of the needle may be releasably coupled but preferably they will be coupled in a non-releasable manner. This may be achieved for example with metallic components by crimping them together.
The IMS device may be arranged to have a gripping mechanism to which the applicator unit may be attached. However, preferably the applicator unit will further comprise an attachment element to allow attachment to the IMS device, the attachment element typically comprising one or more projections for coupling with one or more corresponding elements on the intramuscular stimulation device.
Preferably, the applicator unit will also further comprise a contact block arranged at the rear of the sheath with respect to the first opening, wherein in use, the contact block couples with a corresponding component of the intramuscular stimulation device such that the applicator unit is securely attached to it. For example, a plunger attached to the intramuscular stimulation device may apply a force to the block so as to urge the applicator unit in the first direction.
Typically the applicator unit will further comprise a detent arranged to releasably retain the needle such that the first end portion of the needle is enclosed within the sheath when the applicator unit is not attached to the intramuscular stimulation device.
Preferably the applicator unit according to the first aspect of the present invention will be used in conjunction with a corresponding IMS device.
The use of automatic devices raises safety issues in that the accurate control of the penetration and stimulation cycles should be provided with safeguards such that the patient will not become injured in the event of a device malfunction.
In accordance with a second aspect of the present invention, we provide an intramuscular stimulation device comprising:
a drive carriage to which a needle is coupled in use, the drive carriage being arranged so as to move the needle in a first direction to one of a number of predetermined positions for subsequently performing intramuscular stimulation of a subject;
a drive motor arranged to operate the drive carriage;
a position selecting element arranged to produce a signal identifying the selection of a particular predetermined position from the number of predetermined positions, the signal being used in accordance with the drive motor and drive carriage to move the needle in the first direction to the selected predetermined position; and,
a stop which can be located in accordance with the selected predetermined position so as to prevent the needle from moving past the selected predetermined position.
The IMS device of the second aspect of the invention will be typically used in association with the disposable needle applicator unit according to the first aspect of the present invention.
The selection of predetermined needle positions has associated safety problems and therefore the stop provides a physical safeguard to the further movement of the needle beyond the predetermined position.
Preferably, the drive carriage will be coupled to the needle by the insertion of a portion of the needle in a corresponding hole arranged in the drive carriage. This is particularly convenient when the device is used in conjunction with the needle applicator unit having a second end portion of the needle projecting from the applicator unit sheath.
The drive carriage is typically arranged to be driven to and fro in the first direction by a motor and it may not only provide the motion required for moving the needle to one of the predetermined positions, but also any subsequent reciprocal motion forming part of a mechanical stimulation cycle. Alternatively a stationary drive carriage could be employed, for example having opposed rotatable wheels between which the needle is positioned, such that the needle may be driven to and fro.
When the needle is moved in accordance with the drive carriage, each predetermined position of the needle will correspond to a respective position of the needle will correspond to a respective position of the drive carriage. In order to prevent the movement of the needle beyond the predetermined position in the event of a fault, the stop may be arranged to physically obstruct the motion of the drive carriage past the respective drive carriage position.
The position selecting element may also be arranged at the respective drive carriage positions and the stop may therefore form part of the position selecting element. The position selecting element will preferably comprise sensors located at or adjacent to two or more drive carriage positions. Preferably the sensors will be arranged to detect the presence of the stop, the position of the stop being used not only to obstruct the drive carriage but to select the predetermined needle position.
A pin serves as a suitable stop and the drive carriage positions may be equipped with corresponding pin retaining elements.
The presence of the pin within the pin retaining element may be detected using a Hall effect sensor when the pin has a corresponding magnetic portion.
In addition, the IMS device may further comprise a sensor to detect when the device is correctly located in order to perform an IMS cycle. This may be achieved in connection with an applicator unit where a limited range of movement is provided in the first direction for the applicator unit and a biasing member is also provided to bias the applicator unit towards the front of the device and against the subject""s body. The biasing element will preferably be arranged such that in use, the force of the applicator unit against the body of the patient will overcome the biasing effect such that the applicator unit is moved towards the other end of its range along the first direction.
A reduction in the pressure will therefore cause the movement of the unit towards the body of the patient and this movement may be detected by a sensor arranged to produce a signal to terminate any IMS cycle being performed. An adjustable member may also be provided to adjust the force of this bias.
The movement of the drive carriage will typically be powered by an electric motor and the drive carriage may be arranged to cooperate with a rotating screw member or alternatively a rack and pinion system. In general, the control of the motor will be provided by a microprocessor in communication with the various sensors of the device.
Conventional automatic IMS devices are operated using a foot pedal system in which a depression of the foot pedal when the gun is in the correct position causes a treatment cycle to be initiated. The needle is inserted into the subject and the stimulation is performed followed by the withdrawal of the needle. However, although this proves to be less tiring than the corresponding manual method, the physician may still be susceptible to repetitive strain injury and fatigue as the number of patients treated in one day can be increased.
In accordance with a third aspect of the present invention, we provide a method of controlling an intramuscular stimulation device, the method comprising the steps of:
i) causing the device during an operating time period to take up an active condition in which it can perform an intramuscular stimulation operation; and,
ii) during the operating time period repeatedly determining if a predetermined condition exists for performing an intramuscular stimulation operation and if it does, performing the intramuscular stimulation operation and extending the operating time period.
The method according to this aspect of the present invention therefore reduces the risk of repetitive strain injury and fatigue for the operator of the IMS device. A confirmation signal indicating the existence of the predetermined condition, may be provided by a suitable sensor. In this way, repeated depression of a foot plate or the repeated squeezing of a trigger is avoided. The safety of the system is assured by allowing an IMS operation to be performed only during the time period.
Preferably the step of repeatedly determining if a predetermined condition exists will be performed during the intramuscular stimulation operation in addition to at other times during the operation time period. If during an IMS operation it is determined that the condition is not satisfied then the IMS operation will be terminated and the needle withdrawn.
Typically the predetermined condition will be an indication that the device is correctly positioned against the body of a subject in order to perform an IMS operation.
This may be achieved with a suitable sensor to detect for example when the intramuscular stimulation device is positioned either adjacent to or in contact with the body of a subject.
The method may be arranged such that the IMS operation may be repeatedly performed at one location by reapplying the applicator to the patient. During such a time the predetermined condition allowing the operation of the device may therefore be continually satisfied. However, preferably the method further comprises preventing the performance of a further IMS cycle unless it is determined that the predetermined condition does not exist at a time following the previous IMS cycle. In this way only a single IMS operation can be performed during a period when the predetermined condition is satisfied.
To further enhance safety, the method may further comprise issuing an audible warning prior to each operation of the device.
In accordance with a fourth aspect of the present invention, we provide an intramuscular stimulation unit comprising:
an intramuscular stimulation device to which a needle is attached in use for performing intramuscular stimulation; and
a processor for operating the intramuscular stimulation device according to the method of the third aspect of the present invention.
Such an intramuscular stimulation unit may form part of the system for use in conjunction with a disposable needle applicator unit according to the first aspect of the present invention. In this case the intramuscular stimulation unit may be arranged in accordance with the second aspect of the present invention.